I have just received implants of Iodine125 for medical reasons. The GMC300 works well but when I bring it closer to the source the graph display increases at first but then jumps randomly between the highest and lowest readings. On the Data Viewer the maximum reading is close to 255 in one second. The counter seems to be overflowing. Is the counter firmware limited to 8 bits, ie. 256 counts/sec.?